The field of the invention is passive surveillance systems and, in particular, locating capabilities for underwater acoustic passive surveillance systems.
An underwater surveillance system utilizes a sparse array of underwater sensor nodes spread over a critical area of operational importance. A significant problem with his system is the large amount of data produced by a single field and the very large quantity of noise and unwanted clutter that must be analyzed by a human operator. In essence, each node of the field must be interpreted by an operator to determine which signals are clutter and which may be signals of interest. This is very time consuming and automatic methods of sorting signals and clutter would help save resources.
One approach to eliminating clutter is to segregate all lines associated with a specific platform no matter what the nature of the platform. Then that platform is classified using one or more lines and other expert and collateral information with operators or expert systems. All lines from that source can be placed in a clutter map or track file depending upon its importance. Clutter lines can then be removed from all node displays within the field of view of the sources and alerts automatically sent to other nearby nodes for similar responses.
Acoustic passive ranging is not possible on a single array or between two arrays without ambiguities unless noise like acoustic signals are employed. Using wide band receivers to achieve a noise like signal for inter-array or interbeam triangulation lowers the signal to noise ratio. Also, each beam or array, pointing in different directions, may receive different noise signals in an ocean environment.
Accordingly, it is a feature of the present invention to provide synthesis of a noise like signal that can be used for ranging of passive signals emanating from a target such as a submarine. A noise like signal is required for interarray processing for determining target range by triangulating. Individual sonar frequencies that are detectable may not be noise like and ambiguities would result.
Accordingly, it would be an advance in the art to have a passive surveillance system that provides location information related to sources of signals, and that can automatically locate sources of signals.